1. Field of the Invention
The present invention relates in general to composite framing for building closures, more specifically to framing construction of low thermal transmittance, high strength, and low cost.
2. Description of the Prior Art
Most present day framing members for windows and doors are fabricated from finite lengths of a single material, mainly extruded aluminum, extruded plastic, or wood millwork.
Extruded aluminum offers stiffness and strength, low cost and low maintenance, but has high thermal conductivity. Extruded plastic offers low thermal conductivity, low maintenance and moderate cost, but does not have the stiffness and strength of aluminum. Wood millwork offers low thermal conductivity and reasonable structural qualities, but is higher in cost and requires considerable maintenance.
Preferably a framing member should be a composite of two or more materials, for example, metal and plastic, integrating the best characteristics from each material.
Framing construction art is replete with composite element designs incorporating metals and plastics.
Budich et al. in U.S. Pat. No. 3,703,063, patented Nov. 21, 1972, describes a profile element or windows or doors, comprising a hollow closed metal section surrounded by a shell of plastic for resistance to corrosion and for heat insulation.
He teaches that art prior to his invention includes a great variety of designs having a common disadvantage. It is that the number of basic profiles required for window and door facade assembly is relatively large and that numerous auxiliary profiles are necessary for combining these basic profiles into a flawless, tight connection to the structural component. The Budich profile overcomes this by providing a plurality of projections of-the plastic shell with each projection being for a different application such as a saw-tooth projection for contact with glazing, anchoring means for securing the metal portion to a fixed structure in the form of connecting projections of first and second legs extending in parallel relationship with transverse end portions directed toward each other, and an abutment projection of special shape, for attachment to another Budich profile, so that the profile member has a generally more universally adaptable configuration.
Depending upon their shapes, the projections may be manufactured integrally with the plastic shell, or independently thereof, in which the latter case they are joined to the shell subsequently, for example, by cementing or welding.
U.S. Pat. No. 4,271,634 patented Jun. 9, 1981 by H. Andrzejewski, discloses a metal carrier for channel-shaped sealing, trimming or finishing strip for a channel-shaped window glass guide such as used in automobile window or door openings which resists and limits stretching. It comprises a series of U-shaped metal elements arranged in side-by-side and spaced apart relationship so as to define a channel.
The elements are connected to one another alternately in series by only a link between the apex of the U, or by a pair of links between the legs, one link being on each side of the U.
Each of the legs connected by a link, further includes an extension adjacent to its distal end. The extension terminates in an abutment face that is adjacent to the abutment face of the corresponding connected leg.
The carrier is covered by flexible plastic in which are imbedded the elements, legs, links and abutments. Manufacture is suggested to be by cutting slots in a metal blank by stamping or pressing, then rolling the blank longitudinally in to a U-shape, and after manufacturing the blank, feed the blank into a cross-head extruder so as to cover it with the extruded plastic or rubber.
A tubular seal on one side of the U, along the length of the carrier may be included integrally with the covering, or may be secured to it by some means. In either case it need not be of the same hardness as the carrier covering.
The alternate links permit the carrier to flex during installation, while the abutting extensions prevent or limit stretching of the strip so that it will resile quickly at the time of installation of the strip to a body, for a better and more secure fit.
U.S. Pat. No. 4,569,154 patented by M. Bayer on Feb. 11, 1986, discloses a metal and plastic composite type construction for window framing which, instead of plastic coating over metal, consists of an inside facing plastic extrusion member joined by interconnecting interlocking barbs, darts or arrows to a generally parallel outside facing metal extrusion member. One member is more rigid than the one to which it is joined, and one member has lower thermal conductivity than the one to which it is joined. The shape of the barbs is important to a success of providing a positive lock function for securing the parts together to provide thermal insulation coupled with window strength.
U.S. Pat. No. 4,640,054, patented Feb. 3, 1987 by Breimeier et al., describes a frame for windows or doors which consists of two plastic covered, hollow metal sections, joined by the plastic of their coverings. One section is exposed to the outside environment, the other to the inside environment.
This is different from the art in which a single, plastic covered hollow metal section is exposed to the inside environment on one side, and the outside environment on the other side.
In Breimer's invention, the plastic that is covering and joining the two sections provides thermal insulation. The arrangement permits the two thermally separated hollow aluminum sections to assume different temperatures whereby their elongations and shrinkages have less affect on the neighboring plastic than other designs in the art.
U.S. Pat. No. 4,715,153, patented Dec. 29, 1987 by H. Rohrman, discloses a universal building panel structural frame member which may be used as a head member, side jamb member, sill member, vertical mullion, and horizontal transom member, to form those structures without a need for members of different design, and brackets, plates and bolts to join them.
The invention comprises a unitary elongate roll-formed element that can be cut to length to provide structural members for the above purposes. The element is J-shaped in cross-section, having a flat elongate intermediate plate member, a head on one side of the plate member having portions laterally extending outwardly in opposite directions from the plate member, and a foot member on the opposite side of the plate member laterally extending therefrom. A pair of opposed elongate lips also extend from the plate member.
A preferred embodiment comprises a steel J-shaped member coated with an elastomeric or other thermally insulating coating. The steel adds structural strength without adding bulk. The coating provides thermal insulation without reducing the structural strength of the curtain wall members.
U.S. Pat. No. 4,974,366, patented Dec. 4, 1990 by S. Tizzoni, describes a frame construction for a door opening. The frame includes a reinforced, insulated jamb member which comprises an elongated metal U-shaped channel with one leg being toward the inside environment, and the other leg being toward the outside environment.
The elongated open front end of the channel is closed by a vinyl cover thereby defining with the channel an elongated cavity. An insulating foam is injected into the cavity. After the foam hardens into a rigid and strong insulating core, the back of the U-shaped channel is sawed through lengthwise to establish a metal free insulating space between the legs of the channel.
The rigidity of the jamb is assured by the hardened insulating material between the legs. Retention of the insulating material by the legs is aided by surface grip characteristic of the Isolok TM polyurethane based rigid foam and by flanges along the length of the legs which project into the cavity.
The insulating foam is dense enough to hold hinge screws driven through the vinyl cover and into the foam, and rigid enough to withstand flexion forces exerted by weight of a door on the screws.